Field of the Invention
The present invention relates to a manufacturing method for a bumper beam of a vehicle, and more particularly, to a manufacturing method for a bumper beam of a vehicle, in which a circular pipe is molded into a bumper beam having at least two closed cross-sections through hot stamping molding, to remove a welded portion and prevent a non-uniform dent from being generated on a curvature radius direction inner cross-section by heel tap, even in curvature molding.
Description of Related Art
In general, a bumper beam for a vehicle is manufactured by molding a closed cross-section molding beam, molded through a roll forming method, in a predetermined curvature.
The roll forming method makes the closed cross-section molding beam pass through a roll former unit in which roller formers, that constitute an upper molding roll and a lower molding roll as one pair by unwinding coils, are arranged in multiple-stages in a line to bend and mold the molding beam in various shapes. A detailed system and a detailed process of the roll forming method will be described below.
FIG. 1 is a conceptual view of a general roll forming system and a process for each step thereof.
Referring to FIG. 1, in the general roll forming system and the process thereof, an uncoiler 1 that uncoils a supplied coil 10 is configured in the front of a process line to perform an uncoil step S1.
A straightener 2 that straightens a band-type steel plate released from the uncoiler 1 with a flat-plate steel plate plane 20 is provided in the rear of a process direction of the uncoiler 1 to perform a straightening step S2.
A brake press 3 molding holes for various purposes in the steel plate panel 20 supplied from the straightener 2 is provided in the rear of the process direction of the straightener 2 to perform a piercing step S3.
A roll forming unit 4 formed of roll formers R1 to R7 of at least 10 stages or more (not all are illustrated) is disposed in the rear of the process direction of the brake press 3 to perform a roll forming step S4 of roll-molding the steel plate panel 20 supplied through the uncoiler 1, the straightener 2, and the brake press 3 in a shape of a molding beam 30 having a closed cross-section to be obtained through sequential bend-molding.
A laser welder 5 is provided in the rear of the process direction of the roll forming unit 4 and a laser beam output from a laser oscillator 5a is irradiated to a welded portion of the molding beam 30 to perform a welding step S5.
In addition, a round bender 6 is provided in the rear of the process direction of the laser welder 5 and the molding beam 30 passes through a multi-stage bending roll unit disposed according to a curvature radius, to be molded to perform a bending step S6 of molding the molding beam into a molding beam 40 having a predetermined curvature.
FIG. 2 is a side configuration diagram of a general round bender.
Referring to FIG. 2, the round bender 6 includes 5-stage bending roll units.
A first-stage bending roll unit BR1 is formed of a pair of bending rolls at upper and lower sides in the front of the process direction on a roll frame 6a, to guide the molding beam 30, supplied through a welding step S5, from a molding roll of a rearmost roll former (R7 in FIG. 1) of the roll forming unit 4.
Further, a second-stage bending roll unit BR2 is also formed of a pair of bending rolls at the upper and lower sides in the rear of the process direction of the first-stage bending roll unit BR1 on the roll frame 6a to roll-support the molding beam 30 in a curvature radius direction.
In addition, third, fourth, and fifth bending roll units BR3, BR4, and BR5 are sequentially disposed along a curvature radius to be molded in the rear of the process direction of the second-stage bending roll unit BR2 on the roll frame 6a and each of the bending roll units is also formed of a pair of bending rolls at the upper and lower sides and the molding beam 30 passes through each bending roll unit to be molded into a molding beam 40 having a predetermined curvature.
Moreover, a cutting press 7 is provided in the rear of the process direction of the round bender 6 to perform a cutting step S7 of cutting the molding beam 40 according to a specification of a finished product for producing the molding beam 40.
FIG. 3 is a perspective view of one example of a buffer beam produced through the general roll forming system and process.
Referring to FIG. 3, a vehicular bumper beam 50 by one example produced through the roll forming system and the process thereof is illustrated and the bumper beam 50 by one example is bent to have closed cross-sections at the upper and lower sides and both ends thereof are laser-welded to be molded at a predetermined curvature.
However, as illustrated in FIG. 3, the conventional bumper beam 50 has a problem in that a plurality of dents D in which depths and generation positions are non-uniform is generated on an inner cross-section having a large width in the curvature radius direction due to heel tap during curvature molding through the round bender 6, thereby reducing collision stiffness.
That is, the dents D are generated by deepening the heel tap during forming the curvature by forming a welded portion by welding both ends of the molding beam 30 in a longitudinal direction in the rear of a front surface during the curvature in the welding step S5.
In the case of the non-uniform dent D, when the bumper beam 50 and a towing hook pipe are assembled, a matching property between a hole H formed on the bumper beam 50 and the towing hook pipe is non-uniform to cause a welding error, and as a result, there is a problem in that an additional welding process needs to be performed through a total inspection of the welded portion in order to secure welding qualities of the bumper beam 50 and the towing hook pipe.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.